FIGS. 1 and 2 show continuous belt transport systems that are typically formed from mated carrier plates 102, for a moving sidewalk 100, and carrier steps 202, for an escalator 200. A motor drives the plates 102 and steps 202 in a continuous loop between stationary landings 104, 204. Due to the high traffic on such transport systems, the plates 102 and steps 202 are sturdy, and usually made from steel or cast aluminum, both of which can be heavy. Moving this weight and riders requires a powerful motor.
The powerful motor creates a potential safety hazard, however. At the landings 104, 204, the plates 102 and stairs 202 descending in the continuous loop create a gap between the landings 104, 204 and the last plate 102 or step 202. This gap can catch trash, shoe laces, pointed heels, purse and backpack straps, or even a person's finger or toe. Any of these events could hurt a passenger or damage the escalator.
As a solution to this problem, a combplate serves as the threshold between the landing 104, 204 and the moving stairs 202 or plate 102. The combplate has elongated teeth or fingers, as shown in U.S. Pat. No. 5,718,319, that extend into corresponding grooves in the plates 102 and stairs 202. These fingers discourage objects from being trapped in the gap between the landings 104,204 and last plate 102 or step 202, but due to their location, the teeth/fingers are often damaged by shoes, carts, trash, and misaligned stairs. When this happens, an even more unsafe condition occurs, because the broken teeth/fingers create sharp edges and open spaces where objects can become lodged.
To overcome these problems, plastic combplates with integral plastic teeth/fingers may be used in the threshold area. These plastic combplates have the advantage that they are less expensive to manufacture and replace than cast or machined steel or aluminum, and they provide a cavity for an electronic detection system that detects a finger break and shuts off the motor in response.
Known plastic combplates with integral teeth also have problems. The teeth are weaker and more susceptible to breaking than metal. The circuits within such teeth are expensive to manufacture. And using a single piece plate-and-teeth assembly makes for an expensive replacement because when a tooth breaks, the entire combplate threshold must be replaced.